Question

The postal service sorts mail as Priority Mail Express, Priority Mail, First-Class Mail, or Standard Mail. Over a period of 3 weeks, 18 of each type were mailed from the Network Distribution Center in Atlanta, Georgia, to Des Moines, Iowa. The total delivery time in days was recorded. Minitab was used to perform the ANOVA. The results follow:

Source	DF		SS	MS	F	P
Factor	3		1.83	0.61	2.77	0.048
Error	68		15.28	0.22
Total	71		17.11

Level	N	Mean	StDev
Priority Mail Express	18	2.873	0.477
Priority Mail	18	3.040	0.574
First-Class Mail	18	3.273	0.462
Standard Mail	18	3.228	0.360

Using the ANOVA results, compare the average delivery times of the four different types of mail.

3. What is the decision rule? Use the 0.01 significance level. (Round your answer to 2 decimal places.)

Answer 1

Numerator DF = 3

Denominator DF = 68

Significance level = 0.01

So,

Critical F value = 4.08

Hence,

Decision rule: Reject Ho if F > 4.08